Illinois River basin seasonally dynamic total nitrogen and phosphorus SPARROW model inputs and outputs, 2000 through 2020

This data release contains seasonal source-specific estimates of total nitrogen (TN) and total phosphorus (TP) loading to streams across the Illinois River basin (25,620 reaches) for 21 years from 2000 through 2020 using a dynamic SPARROW (Spatially Referenced Regressions on Watershed attributes) model. Input data including calibration loads, output predictions, model control files, and model source code are provided to fully reproduce results. The modeled period was from December 1999 through November 2020 in seasonal timesteps, or 84 periods, and the following seasonal definitions were applied: winter includes December, January, and February; spring includes March, April, and May; summer includes June, July, and August; and fall includes September, October, and November. See Schmadel and others (2024) for further details.